1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
/* strcpy/stpcpy implementation for x86-64.
Copyright (C) 2002-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <isa-level.h>
#if ISA_SHOULD_BUILD (1)
# include <sysdep.h>
# ifndef STRCPY
# define STRCPY __strcpy_sse2
# endif
.text
ENTRY (STRCPY)
movq %rsi, %rcx /* Source register. */
andl $7, %ecx /* mask alignment bits */
movq %rdi, %rdx /* Duplicate destination pointer. */
jz 5f /* aligned => start loop */
neg %ecx /* We need to align to 8 bytes. */
addl $8,%ecx
/* Search the first bytes directly. */
0:
movb (%rsi), %al /* Fetch a byte */
testb %al, %al /* Is it NUL? */
movb %al, (%rdx) /* Store it */
jz 4f /* If it was NUL, done! */
incq %rsi
incq %rdx
decl %ecx
jnz 0b
5:
movq $0xfefefefefefefeff,%r8
/* Now the sources is aligned. Unfortunately we cannot force
to have both source and destination aligned, so ignore the
alignment of the destination. */
.p2align 4
1:
/* 1st unroll. */
movq (%rsi), %rax /* Read double word (8 bytes). */
addq $8, %rsi /* Adjust pointer for next word. */
movq %rax, %r9 /* Save a copy for NUL finding. */
addq %r8, %r9 /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rax, %r9 /* (word+magic)^word */
orq %r8, %r9 /* set all non-carry bits */
incq %r9 /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
movq %rax, (%rdx) /* Write value to destination. */
addq $8, %rdx /* Adjust pointer. */
/* 2nd unroll. */
movq (%rsi), %rax /* Read double word (8 bytes). */
addq $8, %rsi /* Adjust pointer for next word. */
movq %rax, %r9 /* Save a copy for NUL finding. */
addq %r8, %r9 /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rax, %r9 /* (word+magic)^word */
orq %r8, %r9 /* set all non-carry bits */
incq %r9 /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
movq %rax, (%rdx) /* Write value to destination. */
addq $8, %rdx /* Adjust pointer. */
/* 3rd unroll. */
movq (%rsi), %rax /* Read double word (8 bytes). */
addq $8, %rsi /* Adjust pointer for next word. */
movq %rax, %r9 /* Save a copy for NUL finding. */
addq %r8, %r9 /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rax, %r9 /* (word+magic)^word */
orq %r8, %r9 /* set all non-carry bits */
incq %r9 /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
movq %rax, (%rdx) /* Write value to destination. */
addq $8, %rdx /* Adjust pointer. */
/* 4th unroll. */
movq (%rsi), %rax /* Read double word (8 bytes). */
addq $8, %rsi /* Adjust pointer for next word. */
movq %rax, %r9 /* Save a copy for NUL finding. */
addq %r8, %r9 /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rax, %r9 /* (word+magic)^word */
orq %r8, %r9 /* set all non-carry bits */
incq %r9 /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
movq %rax, (%rdx) /* Write value to destination. */
addq $8, %rdx /* Adjust pointer. */
jmp 1b /* Next iteration. */
/* Do the last few bytes. %rax contains the value to write.
The loop is unrolled twice. */
.p2align 4
3:
/* Note that stpcpy needs to return with the value of the NUL
byte. */
movb %al, (%rdx) /* 1st byte. */
testb %al, %al /* Is it NUL. */
jz 4f /* yes, finish. */
incq %rdx /* Increment destination. */
movb %ah, (%rdx) /* 2nd byte. */
testb %ah, %ah /* Is it NUL?. */
jz 4f /* yes, finish. */
incq %rdx /* Increment destination. */
shrq $16, %rax /* Shift... */
jmp 3b /* and look at next two bytes in %rax. */
4:
# ifdef USE_AS_STPCPY
movq %rdx, %rax /* Destination is return value. */
# else
movq %rdi, %rax /* Source is return value. */
# endif
retq
END (STRCPY)
#endif
|
